#include <bits/stdc++.h>
using namespace std;
int main() 
{
    #ifdef LOCAL
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
        auto start_time = chrono::high_resolution_clock::now();
    #endif
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    // ================ 你的代码从这里开始 ================
    int s=0,n;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        s+=i;
    }
    cout<<s<<endl;
    // ================ 你的代码到这里结束 ================
    
    #ifdef LOCAL
        auto end_time = chrono::high_resolution_clock::now();
        auto duration = chrono::duration_cast<chrono::milliseconds>(end_time - start_time);
        cerr << "Time cost: " << duration.count() << " ms" << endl;
    #endif
    
    return 0;
}